Non-return fuel supply system

ABSTRACT

A return-flow-free fuel supply system for an internal combustion engine having at least one fuel pump for pumping fuel from a first region of a fuel reservoir into a pressure region communicating with a fuel distributor, at least one suction jet pump, through which fuel pumped through a suction jet pump line by means of the fuel pump flows and through which fuel can be pumped from a second region of the fuel reservoir into the first region, at least one means that regulate and/or control the pressure in the pressure region, and at least one check valve, by which at least a portion of the pressure region can be blocked off from the fuel pump. The means that regulate and/or control the pressure in the pressure region include at least one electrically actuatable magnet valve, which is disposed downstream of the check valve in the suction jet pump line.

PRIOR ART

The invention is based on a return-flow-free fuel supply system asgenerically defined by the preamble to claim 1.

In a fuel supply system, fuel from a fuel tank is pumped by a fuel pumpvia a pressure line to a fuel distributor, located on the internalcombustion engine and having injection valves, or to a gasoline orDiesel high-pressure pump. Modern fuel supply systems have a built-intank unit, inserted into the fuel tank, and the fuel pump, an intakefilter, and a pot as a fuel reserve are integrated with it; the pot isfilled with one or more suction jet pumps. The suction jet pumpsconsequently assure that even when the fuel level in the fuel tank isdropping, the pot is always completely filled in order to furnish thereserve fuel. The suction jet pumps are disposed in the suction jet pumpline, which branches off from the pressure line and discharges into thepot.

In modern fuel supply systems, a return line branches off from the fueldistributor and leads back into the fuel tank. The quantity of fuel notneeded by the engine then flows through the fuel distributor back intothe fuel tank via the return line. Conversely, in return-flow-free fuelsupply systems known for instance from German Patent Disclosure DE 19951 132 A1, no return line from the fuel distributor to the fuel tank isprovided. Instead, the fuel in the fuel distributor is regulated asneeded, by measuring the actual fuel pressure with a pressure sensor,comparing it inside a control unit with a set-point fuel pressure storedin a performance graph, and varying the rpm of the fuel pump as afunction of the regulated difference. A check valve in the pressureline, downstream of the fuel pump, assures sealing of the pressureregion that contains the fuel distributor. The regulating function isperformed as long as the engine is operated under load and a quantity offuel to be consumed is called for.

During phases in which the injection valves are closed and the fuel pumpis not pumping fuel into the pressure line, for instance in a stoppedphase of the engine, the pressure in the pressure line which is tight onthe one hand because of the closed injection valves and on the otherbecause of the closed check valve can rise at high temperatures, andtherefore mechanically actuated pressure limiting valves or diaphragmpressure regulators are used to keep the pressure constant in thepressure line. One type of such pressure limiting valves must beconstantly rinsed during operation by a slight overflow quantity, whichon the one hand necessitates constant operation of the fuel pump andconsequently a certain energy consumption; on the other hand, because ofthe slight rinsing quantity, there is the risk that dirt will becomedeposited on the valve seat. Another type of pressure limiting valve isclosed in operation, so that after a nonpumping phase and at the onsetof load operation, because of the sudden pressure rise that then occurs,both excessively rich mixtures and also, because of the higher leakageat the injection valves resulting from the pressure, higher hydrocarbonemissions can occur. Moreover, in both types of pressure limitingvalves, the opening pressure cannot be varied during operation.

ADVANTAGES OF THE INVENTION

Because the means that regulate and/or control the pressure in thepressure region include at least one electrically actuatable magnetvalve which is disposed downstream of the check valve in the suction jetpump line, the magnet valve can be incorporated into the electronicregulation of the engine, which makes it possible to regulate the systempressure and the fuel quantity under all operating states of the engine,and in particular during overrunning and in a stopped phase. Then incontrast to the mechanically hydraulically actuated valves in the priorart, variable opening pressures can be set via the electricallyactuatable magnet valve, depending on its opening duration. This isespecially advantageous to compensate for temperature-caused pressurechanges. Finally, in electrically actuatable magnet valves, therequirement for constant rinsing is eliminated, and therefore the fuelpump can be made smaller, and the risk of soiling of the valve seat isreduced substantially.

By the provisions recited in the dependent claims, advantageousrefinements of and improvements to the invention defined by claim 1 arepossible.

In a preferred way, the magnet valve is disposed between the check valveand the suction jet pump and is triggered by a central engine controlunit; the triggering of the magnet valve is effected as a function ofthe pressure measured by a pressure sensor disposed in the pressureregion. As a result of this provision, the magnet valve is integratedwith the electronic engine control unit, and variable opening pressurescan be achieved as a result. The pressure region communicating withinjection valves is preferably formed by a pressure line which connectsthe fuel pump with the injection valves.

In a first embodiment, an inlet of the magnet valve communicates withthe pressure region, and an outlet communicates with the suction jetpump. In particular, during a stopped phase of the engine the magnetvalve is closed when without current and otherwise, for instance duringnormal operation under load and during overrunning, it is open withcurrent. In the event of a pressure increase, for instance caused bytemperature, during the stopped phase, the magnet valve is opened bysignals from the engine control unit in order to keep the pressure inthe pressure line constant. Because of the electronic regulation of themagnet valve, the holding pressure in particular can be definedarbitrarily during overrunning and when the engine is stopped. However,this also means that the function of the engine control unit must bemaintained temporarily, even during the stopped phase of the engine.

This provision can be dispensed with in a second embodiment, in whichthe magnet valve is formed by a 2/3-way valve, of which an inletcommunicates with the pressure line, a first outlet communicates withthe suction jet pump, and a second outlet communicates with a pressurelimiting valve. This 2/3-way valve is controlled by the engine controlunit such that in a currentless state it connects the inlet with thesecond outlet, while in the state with current it connects the inletwith the first outlet. Consequently, when the engine is stopped and theengine control unit is without current and hence deactivated, the2/3-way valve automatically, for instance by spring prestressing,switches into its currentless position, in which the pressure linecommunicates with the pressure limiting valve, by way of whichoverpressure is then reduced again. In normal operation under load or inengine overrunning, the 2/3-way valve is conversely supplied withcurrent by the engine control unit, so that the suction jet pump isconnected to the pressure line.

In another version of the invention, the triggering of the magnet valveis effected as a function of a filling ratio of fuel in the fuel tankthat forms the second region of the fuel reservoir. Within the fueltank, the pot that receives the fuel pump and then forms the firstregion of the fuel reservoir is provided as a reservoir for the reservefuel. If the magnet valve is closed when the fill level in the fuel tankis in a range between maximum filling and a level which is essentiallyaligned with the upper edge of the pot, then the fuel is no longerpumped from the fuel tank into the pot via the suction jet pump, whichis put out of operation by the closed magnet valve. Instead, to equalizethe levels, the fuel then flows out of the fuel tank into the pot overthe edge of the pot. Given a sufficient filling ratio in the fuel tank,the suction jet pump can consequently be put out of operation, whichresults in a notable reduction in the pumping capacity required of thefuel pump, an increase in system efficiency, less burden on the on-boardelectrical system, less tank heating, and a longer service life of thefuel pump.

A further version provides that the magnet valve is formed by aswitching valve, which is triggered in clocked fashion to regulate thepropellant pressure of the suction jet pump. In an alternative to this,the magnet valve may be a proportional valve, which is triggered toregulate the propellant pressure of the suction jet pump. In both cases,the suction jet pump can always be operated in a range of maximumefficiency.

Consequently, in the sense of a multiple function, the magnet valve notonly serves to provide especially advantageous regulation of the systempressure and fuel quantity during overrunning and when the engine isstopped, but also to attain further energy-saving provisions.

Further advantageous features and refinements of the invention aredescribed in the rest of the dependent claims.

DRAWINGS

Exemplary embodiments of the invention are shown in the drawing andexplained in further detail in the ensuing description. In the drawing,

FIG. 1 is a schematic illustration of a preferred embodiment of a fuelsupply system of the invention;

FIG. 2 is a schematic illustration of a further embodiment of a fuelsupply system of the invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The return-flow-free fuel supply system identified overall by referencenumeral 1 in FIG. 1 serves for instance to supply fuel to an internalcombustion engine of a vehicle, and as its essential components itincludes a built-in tank unit 6, retained inside a swirl pot 2 of a fueltank 4, that includes a fuel pump 8 with an intake filter 10 on theinfeed side, a check valve 14 disposed in a pressure line 12 on thepressure side with respect to the fuel pump 8, and a fuel distributor18, communicating fluidically with injection valves 16, or a gasoline orDiesel high-pressure pump. In a region between the check valve 14 andthe fuel distributor 18, a pressure sensor 20 measures the actualpressure in the pressure line 12 and sends a signal accordingly over asignal line 22 to a control unit, which is preferably formed by acentral engine control unit 24 (MOTRONIC), and in which, as a functionof a regulated difference between the actual pressure and ademand-oriented set-point pressure, a control signal is sent over anelectric line 26 to an electronic fuel pump control unit 30, whichcommunicates with the fuel pump 8 over electric lines 28, in order toreregulate the pressure in the pressure line 12 as needed via the fuelpump 8.

From a portion of the pressure line 12 that is downstream with respectto the check valve 14, a suction jet pump line 34 branches off at abranching point 32; this line, branching off for instance into aplurality of individual lines 36, preferably two of them, contains onesuction pump 38, through which fuel flows, in each branch 36, and theindividual lines 36 discharge into the swirl pot 2. The swirl pot 2serves on the one hand as a fuel reservoir; on the other, in the eventof major lateral acceleration, it briefly prevents the fuel pump 8 fromaspirating any more fuel, because as a consequence of centrifugal forcethis fuel is concentrated in a portion of the fuel tank 4 remote fromthe intake side. In the state in which fuel flows through them, thesuction jet pumps 38 aspirate fuel, from the region of the fuel tank 4located outside the swirl pot, into the two individual lines 36 and in aknown way assure a constant fuel level inside the swirl pot 2.

An electrically actuatable magnet valve 40 is disposed in the suctionjet pump line 34 branching off from the pressure line 12; this magnetvalve is triggered by the central engine control unit 24 via a controlline 42, preferably as a function of the measured pressure in thepressure line 12, the temperature of the fuel, the fill level, and/orengine operating conditions. The magnet valve 40 is embodied so as toopen or close the cross section of the suction jet pump line 34.Preferably, the magnet valve 40 is closed when without current and openwhen with current.

With the above as background, the mode of operation of the fuel supplysystem 1 is as follows: In engine operation under load, the fuel pump 8aspirates fuel from the swirl pot 2; under the influence of the fuelpressure, the fuel stream opens the check valve 14, and some of the fuelstream flows at the branching port 32 into the suction jet pump line 34.In operation under load, the engine control unit 24 supplies current tothe magnet valve 40, whereupon the magnet valve is switched into theopen position, so that the suction jet pumps 38 can aspirate fuel, fromthe region of the fuel tank 4 located outside the swirl pot 2, into theswirl pot 2. The rest of the fuel stream is delivered as needed alongthe pressure line 12 to the fuel distributor 18, so that it can beinjected via the injection valves 16 into combustion chambers of theengine.

In the overrunning mode, the injection valves 16 are closed, so that thefuel stream in the pressure line 12 is equal to zero; at the same time,because the magnet valve 40 continues to be supplied with current and isthus kept open, the suction jet pump line 34 has a flow of fuel throughit and consequently feeds fuel into the swirl pot 2.

Conversely, during a stopped phase of the engine, the engine controlunit 24 switches the magnet valve 40 to be currentless, whereupon themagnet valve closes. Consequently, the portion of the pressure line 12downstream of the check valve 14 and the portion of the suction jet pumpline 34 upstream of the magnet valve 40 are sealed off from theenvironment by the closed injection valves 16, the closed magnet valve40, and the check valve 14 that is closed toward the fuel pump 8, andthe pressure of the fuel quantity present in these portions is supposedto be kept constant. For reasons of temperature, however, the holdingpressure may be too high, which is detected by the pressure sensor 20and reported to the central engine control unit 24. The magnet valve 40is then briefly switched into its open position by the engine controlunit 24, by means of a current pulse, in order to reduce the specifiedholding pressure.

In the second exemplary embodiment of the invention shown in FIG. 2,those elements that remain the same and function the same as in theabove example are identified by the same reference numerals. As themagnet valve, a 2/3-way valve 44 is used here, of which an inlet 46communicates with the pressure line 12, a first outlet 48 communicateswith the suction jet pumps 38, and a second outlet 50 communicates witha pressure limiting valve 52. The 2/3-way valve 44 is triggered by thecentral engine control unit 24 in such a way that in the currentlessstate, it connects the inlet 46 with the second outlet 50, and in thestate supplied with current it connects the inlet 46 with the firstoutlet 48. Preferably, the 2/3-way valve 44 is switched to becurrentless during a stopped phase of the engine, and otherwise, thatis, in operation under load and in overrunning, it is supplied withcurrent. Consequently, upon stoppage of the engine and with the enginecontrol unit 24 deactivated and without current, the 2/3-way valve 44automatically, for instance by spring prestressing, switches into itscurrentless position, in which the pressure line 12 communicates withthe pressure limiting valve 52, by way of which valve overpressure canthen be reduced. In normal operation under load or in the overrunningmode of the engine, conversely, the 2/3-way valve 44 is supplied withcurrent by the engine control unit 24, so that the suction jet pumps 38are connected to the pressure line 12.

In a further development of the first version shown in FIG. 1, thetriggering of the magnet valve 40 is effected as a function of a fuelfilling ratio in the fuel tank 4. If the magnet valve 40 is closed whenthe fill level in the fuel tank 4 is in a range between maximum fillingand a level which is essentially aligned with the upper edge 54 of theswirl pot 2, then the fuel is no longer fed into the swirl pot 2 fromthe fuel tank 4 via the suction jet pumps 38, which have been put out ofoperation because of the closed magnet valve 40. Instead, to equalizethe levels, the fuel then flows out of the fuel tank 4 over the edge 54of the swirl pot 2 and into this swirl pot. Given an adequate fillingratio in the fuel tank 4, the suction jet pumps 38 can consequently beput out of operation. It is furthermore possible to vary the shutoffpressure as a function of the temperature and/or engine operatingconditions.

Both putting the suction jet pumps 38 out of operation and varying theshutoff pressure can also be effected by the 3/2-way valve 44 in thesecond embodiment shown in FIG. 2, if at the above-described, adequatelevel in the fuel tank 4 the magnet valve is switched in such a way thatthe inlet 46 communicates with the second outlet 50, which dischargesinto the pressure limiting valve 52. Then, the part of the suction jetpump line 34 located downstream of the 2/3-way valve 44 is blocked up toa predetermined pressure level, so that the suction jet pumps 38 are nolonger supplied with fuel.

Since in the embodiments of FIG. 1 and FIG. 2 the magnet valves 40, 44are preferably switching valves, they can be triggered in clockedfashion to regulate the propellant pressure of the suction jet pumps 38.In an alternative to this, the magnet valve 40, 44 may also be aproportional valve, which is triggered to regulate the propellantpressure of the suction jet pump. By means of regulating the propellantpressure, the suction jet pumps 38 can then always be operated in arange of maximum efficiency.

1-16. (canceled)
 17. A return-flow-free fuel supply system (1) for aninternal combustion engine, in particular of a motor vehicle, the systemcomprising at least one fuel pump (8), by means of which fuel can bepumped from a first region (2) of a fuel reservoir into a pressureregion (12) communicating with a fuel distributor (18), at least onesuction jet pump (38), through which fuel pumped through a suction jetpump line (34) by means of the fuel pump (8) flows and through whichfuel can be pumped from a second region (4) of the fuel reservoir intothe first region (2), at least one means (20, 24, 30) that regulateand/or control the pressure in the pressure region (12), and at leastone check valve (14), by which at least a portion of the pressure region(12) can be blocked off from the fuel pump (8), the means (20, 24, 30)that regulate and/or control the pressure in the pressure region (12)including at least one electrically actuatable magnet valve (40; 44),disposed downstream of the check valve (14) in the suction jet pump line(34).
 18. The return-flow-free fuel supply system of claim 17, whereinthe magnet valve (40; 44) is disposed between the check valve (14) andthe suction jet pump (38).
 19. The return-flow-free fuel supply systemof claim 17, wherein the magnet valve (40; 44) is triggered by anelectronic engine control unit (24).
 20. The return-flow-free fuelsupply system of claim 18, wherein the magnet valve (40; 44) istriggered by an electronic engine control unit (24).
 21. Thereturn-flow-free fuel supply system of claim 19, further comprising apressure sensor (20) disposed in the pressure region (12), thetriggering of the magnet valve (40; 44) being effected as a function ofthe pressure measured by the pressure sensor (20).
 22. Thereturn-flow-free fuel supply system of claim 20, further comprising apressure sensor (20) disposed in the pressure region (12), thetriggering of the magnet valve (40; 44) being effected as a function ofthe pressure measured by the pressure sensor (20).
 23. Thereturn-flow-free fuel supply system of claim 17, wherein an inlet of themagnet valve (40) communicates with the pressure region (12), and anoutlet of the magnet valve (40) communicates with the suction jet pump(38).
 24. The return-flow-free fuel supply system of claim 23, whereinthe magnet valve (40), during a stopped phase of the engine, is closedwhen without current and is open when with current.
 25. Thereturn-flow-free fuel supply system of claim 17, further comprising apressure limiting valve (52), the magnet valve being formed by a 2/3-wayvalve (44), having an inlet (46) communicating with the pressure region(12), a first outlet (48) communicating with the suction jet pump (38),and a second outlet (50) communicating with the pressure limiting valve(52).
 26. The return-flow-free fuel supply system of claim 25, whereinthe 2/3-way valve (44) is triggered such that in the currentless state,it connects the inlet (46) with the second outlet (50), and in the statewith current it connects the inlet (46) with the first outlet (48). 27.The return-flow-free fuel supply system of claim 25, wherein the 2/3-wayvalve (44) is currentless during a stopped phase of the engine andotherwise is supplied with current.
 28. The return-flow-free fuel supplysystem of claim 17, wherein the pressure region communicating with thefuel distributor (18) is formed by a pressure line (12), which connectsthe fuel pump (8) with injection valves (16).
 29. The return-flow-freefuel supply system of claim 28, wherein the suction jet pump line (34)branches off from the pressure line (12) downstream of the check valve(14).
 30. The return-flow-free fuel supply system of claim 17, whereinthat the triggering of the magnet valve (40; 44) is effected as afunction of a fuel filling ratio of the second region (4) of the fuelreservoir.
 31. The return-flow-free fuel supply system of claim 18,wherein that the triggering of the magnet valve (40; 44) is effected asa function of a fuel filling ratio of the second region (4) of the fuelreservoir.
 32. The return-flow-free fuel supply system of claim 19,wherein that the triggering of the magnet valve (40; 44) is effected asa function of a fuel filling ratio of the second region (4) of the fuelreservoir.
 33. The return-flow-free fuel supply system of claim 30,wherein the first region of the fuel reservoir is formed by a pot (2)that receives the fuel pump (8) and is disposed inside the second region(4) of the fuel reservoir.
 34. The return-flow-free fuel supply systemof claim 33, wherein the magnet valve (40; 44) is closed when the liquidlevel in the second region (4) of the fuel reservoir is in a rangebetween maximum filling and a level which is essentially level with anupper edge of the pot, and that otherwise it is open.
 35. Thereturn-flow-free fuel supply system of claim 17, wherein the magnetvalve (40; 44) is formed by a switching valve, which is triggered inclocked fashion for regulating the propellant pressure of the suctionjet pump (38).
 36. The return-flow-free fuel supply system of claim 17,wherein the magnet valve is formed by a proportional valve (40; 44),which is triggered for regulating the propellant pressure of the suctionjet pump (38).